fatboySIM by 1935711
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1935711 Presents
fatboySIM
Size ... : .............. 6331 Bytes
Date ... : .............. 2023-08-26
Party .. : ............. Xenium 2023
Compo .. : .................... Wild
Platform : . sysmoISIM-SJA2 SIM Card
Mobile operators who provide you with a
SIM card, may install cardlets (Java
Card applets) onto it. Not all cards
contain a Java Card Runtime Environment
(JCRE) and/or allow for cardlet
installation, but if it does, the
operator may even install these
remotely over the network (without your
permission).
This demo is a cardlet which can be
installed on real SIM cards (granted
you have the key material of your card,
i.e. the KIc and KID).
What you see is indeed rendered by the
SIM. Well, the SIM does render every
single frame, but it packages this
frame into a 'SET UP MENU' command
which is sent to the phone. The phone
interprets this data and renders it 1:1
how it was described by the SIM.
Every line of the frame is one menu
item, and each column is a character in
a menu item.
The tone that you'll hear are
preprogrammed on the terminal (your
phone), and are standardized to sound
exactly the same on all phones. In many
ways, this demo is extremely portable,
it will work on every phone that has
the SIM toolkit app (even old feature
phones have it).
You might wonder why the frame rate is
so low and unstable. There are a couple
reasons, first of all, the messages
sent to/received from the SIM are
actually received by a separate
computer, namely the modem in your
phone, and then forwarded to the
application processor that runs your
Android, etc. The second reason is that
because the SIM itself is also a fairly
complex computer, it contains an OS.
The OS is what triggers our cardlet to
render another frame and it does so by
sending it events. There are two main
events, the first is the
'EVENT_STATUS_COMMAND' which occurs
when the phone sends a 'STATUS'
command. It does so at frequency of
roughly 0.5-1 hz. The second is
'EVENT_MENU_SELECTION', which gets sent
every time you press one of the items
in the SIM toolkit menu. Since the
status message is sent rarely, we can
speed up the demo by repetedly pressing
the items in the menu (I automated this
with ADB on Android when making the
recording).
After each 'SET UP MENU' command sent
by the SIM, the terminal responds
with a 'TERMINAL RESPONSE'. To make the
framerate decent, one would have to be
able to send a '91XX' status as a
response to every terminal-sent
command. This way, the terminal would
keep fetching a new frame as fast as
possible, with no additional overhead,
and without tapping the screen...
Thanks:
nisereth
malpa
lechu
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